The human visual system is capable of identifying and processing visual features with a high degree of dynamic range. Dynamic range generally refers to the range of light intensities from the darkest shadows to the brightest highlights. For example, real-world scenes with contrast ratios of 1,000,000:1 or greater can be accurately processed by the human visual cortex. The human eye, through adaptation of the iris and other methods, adjusts constantly to the broad dynamic changes ubiquitous in our environment. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions.
Most image acquisition devices, however, have limited High Dynamic Range (HDR) imaging capabilities. Some cameras are only capable of reproducing or capturing Low Dynamic Range (LDR), resulting in a loss of image accuracy and failure to capture the image as the human eye would see it. For example, traditional photography includes capturing of images in a scene at a single exposure level in the imaging device, resulting in an image with a limited contrast range. The limited contrast (or dynamic) range results in a loss of detail in bright areas of a picture (if the imaging device used one exposure setting) and/or a loss of detail in dark areas (if the imaging device used a different exposure setting). A common example of this effect is a photograph in which the sky appears almost white, while objects on the ground are exposed sufficiently so as to allow details of those objects to be seen. In other words, when taking a picture in the high contrast environment, original colors, original tones, and original details appearing in an actual scene may almost disappear in a high illumination area or a low illumination area.
In an attempt to overcome the disadvantages described above, some image acquisition devices have been designed to capture several frames of the same scene while changing the exposure from frame to frame, then utilizing post-processing techniques to fuse the captured frames together in an attempt to generate an HDR image. However, when the camera, or a subject, or an object of a background is moving during image acquisition, deterioration may be caused by such motion during the HDR fusion process, as the captured frames are different from one another. Thus, a significant problem with conventional methods is the inability to produce HDR images in real, or near-real time, further limiting the ability of image acquisition devices to provide HDR video imaging. Furthermore, current HDR imaging systems may be bulky and thus may not lend themselves for use in smaller, more compact image acquisition devices.